1. Field of the Invention
The present invention concerns a bi-directional radio frequency (RF) communication apparatus, which is particularly suitable for use in an interactive satellite television system.
The use of satellites to distribute television signals is known in the broadcasting industry and has helped revolutionize television distribution systems. The first generation of satellite television systems have employed communication satellites that encircle the earth in so-called “geosynchronous” orbits, meaning that the satellites encircle the earth and appear to be stationary relative to fixed points on earth. Such geosynchronous satellites typically maintain a high altitude which enables a single satellite to distribute television signals to entire continents or large portions of continents.
2. Background Information
The next generation of satellite television systems propose use of low earth orbit (“LEO”) satellites which occupy much lower orbits than geosynchronous satellites. In particular, a LEO satellite system is conducive for providing various interactive services, such as interactive television services, internet services (e.g., electronic mail, web surfing, etc.) and the like, since the round-trip signal propagation time between an LEO satellite and a receiving location on the earth is substantially less than that in a geosynchronous satellite system. However, because of their lower orbits, multiple LEO satellites are required in order to distribute signals to a particular geographical area which may sufficiently be covered by only a single satellite in case of a geosynchronous satellite system. Accordingly, the use of multiple LEO satellites requires that a user's system be capable of tracking a plurality of moving satellites and receiving signals from such satellites without any disruption. Thus, a user's system should include a plurality of signal receiving modules which corresponds to the respective plurality of LEO satellites and requires that these receiving modules operate in a coordinated manner. In addition, in order to accommodate the interactive services, it is also desirable for a user's system to include a means for transmitting signals to the satellites. The present invention addresses these and other issues.